where \(v(x,t)\)  is the fluid velocity; \({P}(x,t)\)  is the macroscopic pressure; \(\omega _i\)  are weighting factors (whose values are adopted from [1]}); and \(\mathbf {b}(\mathbf {x},t)\)  is the force density in Eulerian coordinates. Pressure \({P}(x,t)\)  and velocity \(\mathbf {v}(x,t)\)  can be calculated from the distribution functions \(f_i(x,t)\)  via the expressions
\(P(x,t)=c_s^2\sum _if_i(x,t),\) 
\(v(x,t)=\frac{1}{\rho }\sum _ie_if_i(x,t)+\frac{1}{2\rho }b(x,t)\Delta t.\) 
